How Often Should You Change Fish Tank Filter | Answer, Tips & Tricks

Maintaining a fish tank is not as difficult as one might think. Still, some essential aspects of care must be followed in order to keep your fish healthy and happy.

Your fish tank filter is one of the most important aspects of fish keeping. If you don’t do it properly, you could end up with a lot of dirty water and sick fish.

One of the most important things to remember is how often you should change your fish tank filter.

In this blog post, I’ll discuss tips and tricks on how to properly maintain your filter – and how often should you change fish tank filter for optimal results!

How Often Should You Change Fish Tank Filter?

When you buy a good-quality fish tank filter, you won’t have to replace the actual filter unless it stops working. The filter machine will continue to function year after year. 

What you have to change is the filter media. How often you need to change aquarium filter media depends on what sort of filter you’re using. 

Some filters need replacing more frequently than others.

Filter media are three types: mechanical, biological, & chemical filter media.

Mecahnical Filter Media

The most common type of mechanical filter media is filter foam. The filter foam is inserted into the filter to capture large debris to minute dirt particles.

The mechanical filter media keeps the fish tank free of unnecessary and harmful materials and maintains crystal clear water. It won’t need to be replaced until the media falls apart or the filter stops working.

Mechanical filter media should not be changed or substituted unnecessarily. Over time the foam material gets covered with beneficial bacteria that work as biological filtration.

Related Read: Changing Aquarium Filter Without Losing Bacteria

When to replace mechanical filter media

When you replace the media, that means you are removing good bacteria. Therefore you shouldn’t do that until it’s due. However, as it continuously sucks debris, it becomes clogged frequently.

So, you need to clean the mechanical filter foam or sponge every two to four weeks, depending on the bioload of your aquarium.

Never clean the filter foam under tap water, as tap water may contain chlorine which can kill the beneficial bacteria. Instead, use the old aquarium water to clean the filter sponge.

Read More: How to Clean Filter Sponge (Most Effective Techniques)

Biological Filter Media

The most common type of biological filter media is bio balls or ceramic rings. Those are placed in the filter to provide a large surface area for beneficial bacteria to grow.

When to replace Bio media

The bacteria on the biological media break down ammonia and nitrites in the water, which keeps the water healthy and safe for your fish.

The bio-media should be replaced every six to twelve months or when they start to fall apart. Apart from the changing schedule, the aquarium filter needs to be cleaned monthly or at least every two months.

Chemical Filter Media

Activated carbon is the most common type of chemical filter media. It’s used to remove dissolved organic waste, toxins, and medications from the water.

Activated carbon should be replaced every four to six weeks.

When to replace Chemical Filter media

You might need to replace your filter media more frequently if you have a lot of fish in your aquarium or if you don’t clean your aquarium regularly.

If you have a tiny aquarium, you might be able to get away with changing the filter media less frequently.

It’s important to keep an eye on your water quality and make sure you’re changing the filter media frequently enough to keep your water clean and safe for your fish.

Factors To Look At When You Have To Change The Filter Itself

Even though you might not have to replace the filter itself very often, a few factors can cause you to need a new one sooner.

  • If your filter starts making strange noises, that’s a sign that it’s not working correctly, and you might need a new one.
  • If your filter starts leaking, that’s another sign that it might be time for a new one.
  • If you notice that your water quality is declining, even after you’ve changed the filter media, that’s a sign that you might need a new filter.

Before replacing the entire filter, you should look after into few things so that your fish remains happy & healthy during the changeover process.

Most of the time, aquarists immediately dispose of the old aquarium filters after buying a new one. They only think about installing the filter but completely overlook the one major thing- the bacteria that cover the previous filter. 

Consequently, they get crystal clear water in no time, but their fish health is affected. Missing beneficial bacteria may prove fatal to fish also. As you remove the old one suddenly, the nitrogen cycle disrupts, resulting in fish suffering.

Therefore, you have to find a way to preserve the bacteria while replacing the fish tank filter.

You can do that in a few simple ways: 

  • If your new aquarium filter comes with its own media, then simply place some of the old one on top of the new one. At least run this way up to two-three weeks so that bacteria gets enough time to colonize in the new filter media.
  • Run both the filter at a time for at least two-three weeks (If the old one is still operable). That way, nothing will be disrupted, and over filtration isn’t harmful. Over time bacteria will start to colonize in the new filter media.
  • During this transition, you must check the chemical filter setting to ensure it is the same as the aquarium’s specification. It is critical that the nitrogen, ammonia, and nitrate levels remain stable.

Related Article: The Right Way to Install Fish Tank Filter Cartridge


The maintenance of the fish tank filter is highly important. Monitoring the fish behavior and water parameters is an excellent way to know whether your filter is doing its job.

Biological crashes and other issues that result from faulty or damaged filters can be prevented with constant maintenance. The presence of ammonia in the water can make fishes suffer from harmful effects.

Cleaning and replacing the filter media is crucial to sustaining the healthy ecosystem in your aquarium.

That’s it! I hope this article helped answer your question of how often should I change a fish tank filter.

If you have any additional questions, please leave them in the comments below, and I will do my best to answer them. Have a great day and happy fish keeping!

Sujit Modak

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